The present invention relates to a novel amine-modified polyester and to a unique formulation of photocurable binder and coating composition composed of the amine-modified amorphous linear aromatic polyester in combination with photopolymerizable unsaturated monomer.
U.S. Pat. No. 3,624,181 discloses certain amine-modified polyesters which are useful for the formation of fibers which are dyeable with acid dyes. The polyester is derived from terephthalic acid and glycol, the whole or the major portion of which glycol is comprised of a glycol containing a tertiary amino group. The inclusion of units derived from 1,2-propanediol is not specifically disclosed.
Previous work has further shown that linear amorphous polyesters derived from terephthalic acid and 1,2-propanediol or terephthalic acid and mixtures of 1,2-propanediol and ethylene glycol are applicable as binders for UV curable systems. For example, U.S. Pat. No. 4,110,187 discloses an untraviolet radiation curable composition comprising a solution of 5-50% by weight of a polyester of terephthalic acid esters and a glycol of about 60-100 mole percent 1,2-propylene glycol and 0-40 mole percent ethylene glycol. The disclosed polyesters do not contain tertiary amino groups. The disclosed composition further comprises 95-50% by weight of an ethylenically unsaturated photopolymerizable compound.
Combinations of an aromatic ketone and a tertiary amine have also been described in the prior art. See, for example, U.S. Pat. Nos. 3,673,140, 3,759,807, 3,847,771, and 3,759,809.
None of the prior art mentioned above describes the novel polyester of the present invention or a UV curable coating composition containing an amorphous aromatic polyester having a pendent tertiary amine group, as is provided by the present invention.
The novel amine-modified polyester is useful in the formation of ultraviolet radiation curable coatings and inks. In the coating composition of the present invention, the amine-modified amorphous linear aromatic polyester functions as a crosslinkable resin and also as a component of the photoinitiation system. The coating composition of the present invention obviates the necessity of utilizing a photoinitiator system which comprises a combination of aromatic ketone and a tertiary amine in addition to the polyester resin.
The coating composition of the present invention is useful as a binder and gives clear insoluble coatings which are applicable as protective and/or decorative coatings for substrates such as wood, glass, aluminum, paper, and plastics. When coated on a suitable substrate, a tough glossy finish is obtained when exposed to UV radiation. The hardness and solvent resistance of the finish can be varied by the use of polyfunctional comonomers. These unique formulations release no solvents into the atmosphere and require no heat energy for curing.